Solid state light sources may be utilized to provide colored or white LED light (e.g., perceived as being white or near-white), as has been investigated as potential replacements for white incandescent lamps. Solid state light sources are particularly desirable for their potentially high efficiency and long life relative to other (e.g., incandescent, halogen, fluorescent, etc.) light sources. A solid state lighting device may include, for example, at least one organic or inorganic light emitting diode (“LED”) or a laser, optionally coated with at least one phosphor to achieve a desired color or combination of colors. Combined emissions from multiple solid state and/or phosphor emitters (e.g., blue+yellow, red+green+blue, or other suitable color combinations) may be perceived by a viewer as white light. Various methods for generating white light from solid state emitters and phosphors are further disclosed in U.S. Pat. No. 7,213,940, which is hereby incorporated by reference as if set forth fully herein.
Given the enormous installed base of incandescent lamps and light fixtures having threaded Edison-type sockets, a substantial financial incentive exists for manufacturers to produce solid state lamps capable of being retrofitted into existing Edison-type threaded fixtures. Edison-type threaded sockets are conventionally used to power incandescent light bulbs from an AC power source, with such a socket arranged to mate with a male base including a screw thread contact and an electrical foot contact.
Solid state emitters require constant current to maintain proper light emission. If current to a solid state emitter varies, the luminous intensity and chromaticity may vary (e.g., white LEDs may shift toward blue in color) and excessive heating may result, potentially leading to shortened life or damage. White LEDs are conventionally powered in different ways, including: (a) a current source and ballast resistors; (b) multiple current sources; and (c) a current source (e.g., inductor-based boost converter) with multiple LEDs in series connection. Each of the foregoing power circuit types are advantageously implemented with components mounted to a printed circuit board (PCB), optionally including at least one integrated circuit and/or processor. Dimming is also a concern for white LED emitters, since standard TRIAC-based dimming schemes applicable to incandescent lamps are not directly applicable to LEDs. LED dimming is typically done through pulse width modulation (PWM), rather than TRIAC-based dimming (which delays turning on energy to a bulb following every zero crossing of an AC power source). To enable white light LEDs to interface with TRIAC-based dimmers, a driver circuit (such as the National Semiconductor LM3445) can be used to monitor the waveform from a standard TRIAC dimmer and adjust same to supply the correct PWM duty cycle and current. Such driver circuitry is also desirably implemented with components mounted to a PCB. Further control circuitry may be associated with a PCB to adjust color and/or chromaticity of solid state emitters. A PCB and associated circuitry may be desirably contained within a housing (or envelope) of a solid state lighting device to protect the circuitry from impact and/or exposure to ambient conditions.
With reference to FIGS. 1A-1C, a conventional method for assembling a threaded Edison base solid state lighting device having a PCB involves multiple steps, including establishment of electrical connections to the PCB. FIG. 1A depicts a PCB 10, a housing 20, and an Edison cap 30. The PCB 10 has electrical components 15 mounted thereon and interface wires 11, 12, to form a PCB assembly 5. The housing 20 includes a first open end 21, a second open end 22, and progressively larger stepped first, second, and third body portions 25A-25C with intermediate transitions or shoulders 26A-26B therebetween. Screw threads 24 are provided on a lateral surface of the first body portion 26A. The housing 20 defines a cavity or hollow interior 29. An attachment lug 28 including an aperture 28 protrudes outward from the third body portion 25C. The generally cylindrical Edison cap 30 includes a threaded sidewall contact 34, an insulating transition 33, and a protruding foot contact 32 defining an aperture 31 therein. A first step in establishing electrical connection to the PCB 10 and components 15 thereon includes soldering the two interface wires 11, 12 to the PCB 10 (e.g., for line and neutral connections). Next, the PCB assembly 5 is inserted into the cavity 29 of the housing 20 and the wires 11, 12, are routed out of the open top end 21. As shown in FIG. 1B, one wire 11 is routed against the first body portion 25A to mate with the threads 24, and the other wire 12 is routed through the interior of the Edison cap 30 to project through the aperture 31 defined in the foot contact 32. The Edison cap 30 is then screwed into position (as shown in FIG. 1C) to engage the threads 24 and enclose the first end 21 of the housing 20, with the wires 11, 12, protruding from the bottom of the sidewall 34 and from the aperture 31, respectively. Thereafter the two wires 11, 12, are soldered in their respective positions and trimmed flush to the solder joints (not shown). The foregoing steps in combination are not susceptible to inexpensive automation, and therefore require substantial labor for completion thereof.
A solid state lighting device 60 comprising the PCB 10 with components 15, the housing 20, and the Edison cap 30 is illustrated in FIGS. 2A-2B. In addition to the components described in connection with FIGS. 1A-1C, the lighting device 60 includes fins 40 associated with the body 20 to dissipate heat generated by the lighting device 60, a reflector 40 disposed below the PCB 10, at least one solid state light emitting element 50 arranged to emit light toward the reflector 40, at least one support 42 for the at least one light emitting element 50, a lens 48, and a peripheral ring or bezel 43 disposed along an emitting end 44 of the device 60.
Other electrical devices having PCBs are fabricated by soldering wires between PCB and externally accessible electrical connectors. Establishing such soldered connections is labor-intensive and provides potential for fabrication errors.
It is known to conduct DC supply power to low-current devices through universal serial bus (USB) connectors that include metalized contacts on an insulating substrate. USB connectors are well-suited for charging and/or powering low-current devices, but are generally not used to conduct AC power, and further may not be well-suited for light fixtures or applications requiring electrical currents exceeding one or more amperes.
It would be desirable to reduce the labor associated with conventional methods for establishing electrical connections to a PCB during assembly of electrical devices, including threaded Edison base solid state lighting devices. It would also be desirable to improve the reliability of such electrical connections, and improve manufacturing yield.